The Assignee of the present invention manufactures self-excited electrical power generators for use in airframes which utilize a permanent magnet generator for generating a field for an excitor generator which generates alternating current which is rectified by a diode assembly to produce the field for the main generator. Oil is utilized as a cooling medium which is circulated through the diode assembly of the generating system for rectifying the alternating current produced by the excitor generator and through the rotor of the main generator for dissipating heat. The oil cooling permits the diode assembly and windings of the rotor of the main generator to be driven with higher currents which permit higher outputs. The leakage of oil into the air gap between the stator of the main generator and the rotor of the main generator creates windage losses.
Examples of fluid cooled electric generators are disclosed in U. S. Pat. Nos. 2,894,155, 2,897,383, 3,439,201, 3,469,127, 4,647,805 and 4,728,840. None of these systems utilizes a sleeve for containing coolant fluid from migrating radially outward from a rotor to the air gap between the rotor and the stator. As a result, leakage of coolant fluid can cause reduced efficiency especially in view of the natural propensity of oil which is the typical coolant used in cooling generators to leak from a coolant flow path.
U. S. patent application Ser. No. 765,017, entitled "Structurally Tailored Non-Metallic Stator Cooling Fluid Containment Sleeve" filed on Sep. 24, 1991, which is assigned to the Assignee of the present invention, discloses a sleeve which is press fit into the annulus of a stator which is formed from a plurality of laminations. The sleeve performs numerous functions including the containing of oil from flowing from the windings of the stator into the air gap between the stator and the rotor. As a result, the sleeve provides effective oil containment to prevent leakage of oil into the air gap between the inner diameter of the sleeve and the outer diameter of the rotor of the electric machine.
Electrical power generators which are manufactured by the Assignee for use in airframes have utilized spray cooling of oil of the excitor rotor. Spray cooling of the rotor of the excitor creates leakage of the oil into the air gap between the rotor and the stator of the excitor which reduces efficiency as a consequence of windage losses. Moreover, spray cooling does not immerse the windings of the rotor of the excitor in oil which reduces the overall efficiency of cooling over that which would be realized if a mechanism existed for containing the windings of the excitor rotor immersed in oil.